[Not Applicable]
1. Field of the Invention
The present invention relates to investment cast molding tools for the manufacture of golf club heads. More specifically, the present invention relates to an investment cast molding tool for one-piece construction of hollow metal wood-type golf club heads.
2. Description of the Related Art
One of the oldest methods of forming golf club heads is through investment casting. This process is currently used to produce the majority of wood-type golf club heads. In this process, a resin mold, which includes two plates composed of aluminum hinged at one end and having a hollow center, is used. A master copy of the golf club head to be produced is suspended in the hollow center and a liquid resin is poured around the master copy to create the outer shape of the golf club head upon solidification of the resin.
In hollow metal wood-type golf club heads, the interior shape of the golf club head is produced by an aluminum core, which typically consists of five pieces. Wax is injected into the mold to fill the space between the inner and outer shapes of the golf club head. The mold is opened and the aluminum core with the wax around it is removed. The aluminum core is separated from the wax by first removing a center piece of the core. The remaining pieces of the core are then removed through the opening that was created by removal of the center core piece. When all of the pieces of the core are removed, the golf club head will have a large opening in either the crown or sole, through which the aluminum core was removed. This opening is then covered by a plate, which is typically welded about its perimeter to the golf club head. The weld must then be sanded smooth to blend with the rest of the golf club head. This sometimes leads to walls that either are too thin or have unexpected variations in thickness. Additionally, sometimes slag or pieces of the weld will fall into the hollow interior of the golf club head leading to unwanted rattling in the club head.
Thus, there is a need for an improved apparatus and method for forming hollow golf club heads. The preferred apparatus and method eliminate the use of multi-piece aluminum cores, which require a large opening in either the crown or sole of the-golf club head.
The present invention is a replacement to the use of molds with multi-piece aluminum cores. In accordance with the present invention, an apparatus includes a first mold, a second mold, a ceramic core, and means for injecting wax. The first mold has a cavity with a plurality of depressions formed therein. Each of the depressions has a depth substantially equal to the wall thickness of a corresponding portion of the desired golf club head. When the ceramic core, which has an exterior surface that corresponds to an interior of the golf club head, is inserted into the first mold cavity and wax is injected, wax protuberances corresponding to the depressions are formed about the exterior surface of the ceramic core. The ceramic core with the wax protuberances is then removed from the first mold and placed in the second mold. The second mold has a cavity that is complementary in shape to the exterior of the desired golf club head. The wax protuberances properly situate the ceramic core completely within the second mold cavity to ensure that the walls of the resulting golf club head have the correct thicknesses. Wax is then injected into the second mold cavity. The wax adheres to the wax protuberances and to a majority of the exterior surface of the ceramic core. The wax-covered ceramic core is then removed from the second mold. A shell is formed over the wax, and the wax is melted, leaving a gap between the shell and the ceramic core. Molten metal is then cast into the gap to form the golf club head. After metal has cooled, ultrasonic vibration may be used to break up the ceramic core and remove it from the interior of the golf club head.
Having briefly described the present invention, the above and further objects, features and advantages thereof will be recognized by those skilled in the pertinent art from the following detailed description of the invention when taken in conjunction with the accompanying drawings.